The prior art reveals a variety of mechanisms for deflecting articles travelling along a conveyor belt laterally. These range from simple gates which are lowered into the path of the article to more complicated devices which comprise pushers or extensors which travel with the belt. These second species of mechanisms typically allow for selective deflection of even closely spaced items travelling along the conveyor belt. This allows for particular articles from a stream of articles to be selectively deflected, for example when the article fails some sort of quality control check, such as a bottle which is not completely filled or the like.
In particular, the prior art discloses mechanisms comprised of a plurality of extensors or segments which may be individually extended or retracted by pneumatic pistons. The distance of travel of subsequent segments is greater than that of the previous segments, thereby providing for a steadily increasing deflection. Typically, the segments have an angled deflection face which comes into contact with the article. The segments are sequentially extended into the path of travel of the article to be deflected and may be immediately retracted subsequent the deflection in order to not foul the path of travel of a subsequent article. In order to control the extension and retraction of the pistons, such prior art devices take advantage of a plurality of electronically controlled valves and a source of compressed air.
One drawback of these prior art devices is that the width of the segments is limited by the positioning of the pistons relative to one another. In particular, the cylinders which house the pistons each comprise a pair of collars to which the air hoses are attached. These collars are relatively large and limit how proximate pistons can be placed relative to one another. In order to overcome this drawback, the prior art discloses valves which are arranged in a staggered format. However, this has the added drawback that the pistons are difficult to access for maintenance, adjustment and the like.
Another drawback of these prior art devices is that the speed of the pistons may vary over time due to the effects of wear and tear, dirt and the like. This in turn affects the accuracy if the mechanism and must be compensated for, typically through manual calibration.